The Spin-Kinetic Temperature Coupling and the Heating Rate due to Lyα Scattering before Reionization: Predictions for 21 Centimeter Emission and Absorption

By Xuelei Chen, J. Miralda-Escudé. 2003

214 citations recorded by the source corpus.

We investigate the interaction of Lyα photons produced by the first stars in the universe with intergalactic hydrogen prior to reionization. The background Lyα spectral profile is obtained by solving a Fokker-Planck equation. We present accurate values of the heating and scattering rates and the spin-kinetic temperature coupling coefficient. We show that the heating rate induced by the Lyα scattering is much lower than found previously and is basically negligible. The dominant heating source is most likely X-rays from the first ionizing sources, which are able to penetrate into the atomic medium. The scattering of Lyα photons couples the hydrogen spin temperature to the kinetic temperature. If the first ionizing sources in the universe did not emit significant X-rays, the spin temperature would be rapidly brought down to the very low gas kinetic temperature, and a 21 cm absorption signal against the cosmic microwave background (CMB) larger than 100 mK would be predicted. However, we argue that sufficient X-rays are likely to have been emitted by the first stellar population, implying that the gas kinetic temperature should rapidly increase, turning a reduced and brief absorption signal into emission, with a smaller amplitude of ~20 mK. The detection of the 21 cm absorption and emission features would be a hallmark in unravelling the history of the "dark age" before reionization.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/eb600f453f65c65d7f2264dd27d58e266d5e97bc

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Citations in the corpus

New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7 (2013, methodology): “…sufficient to couple the spin and kinetic temperatures throughout the neutral IGM via the Wouthuysen-Field effect, but they do not substantially heat the gas (Chen & Miralda-Escudé 2004), nor do supernovae, X-ray binaries, or mini-quasars produce enough X-rays to heat the large scale neutral IGM.”
Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch of Reionization (2005, background): “In addition, it is expected that at higher redshifts than those considered here, X-ray photons and shocks heat the gas in the IGM to well above the CMB temperature (Venkatesan et al. 2001; Chen & Miralda-Escudé 2004).”
The global 21-centimeter background from high redshifts (2006, background): “The coupling coefficient is (Chen & Miralda-Escudé 2004; Hirata 2006) xα = 1.81 × 1011(1 + z)−1 Sα Jα, (3) where Sα is a factor of order unity describing the detailed atomic physics of the scattering process and Jα is the background flux at the Lyα frequency (neglecting scattering) in units cm−2…”
Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries (2016, background): “…Lyα background photons to mix the hyperfine levels and of a pre-heating mechanism, such as X-ray radiation from the first galaxies or AGNs (e.g., Field 1958; Madau et al. 1997; Ciardi & Madau 2003; Chen & Miralda-Escudé 2004; Kuhlen et al. 2006; Furlanetto 2006; Pritchard & Furlanetto 2007).”
21 cm cosmology in the 21st century (2011, background): “This spectral distortion is a part of the photons coming into equilibrium with the gas and serves to greatly reduce the heating rate [29, 31, 32, 52].”
Simulations and Analytic Calculations of Bubble Growth during Hydrogen Reionization (2006, background): “At the redshifts we consider presently, the 21 cm excitation temperature is likely coupled to the gas temperature, and much larger than the temperature of the CMB (e.g. Furlanetto 2006; Chen & Miralda-Escude 2004; Ciardi & Madau 2003), TS >> TCMB, implying δT ∝ (1 + δs)xH .”
The physics of the intergalactic medium (2007, background): “…a Lyα intensity of Jα ≃ 0.6S−1α × 10−24 W m−2 Hz−1 sr−1, where Sα is a suppression factor of order unity that takes into account the effect of recoils in an expanding medium on the shape of the intensity near the center of the line profile (Chen and Miralda-Escudé, 2004; Furlanetto et al., 2006).”
Observational Constraints on Cosmic Reionization (2006, unknown): “Rev. D., 70, 043502 Chen & Miralda-Escude 2004Chen, X. & Miralda-Escude, J. 2004, ApJ, 602, 1-11 Chiu et al. 2003Chiu, W. A., Fan, X., & Ostriker, J. P. 2003, ApJ, 59 9.”
Science with the Murchison Widefield Array (2012, background): “…mechanisms that affect the hyperfine level populations: the ambient radiation at 21 cm due to the CMB with Tγ , the ultraviolet background that tends to drive TS to the gas temperature (Wouthuysen 1952; Field 1958), and heating from the cosmological X-ray background (Chen & Miralda-Escudé 2004).”
Fast large volume simulations of the 21-cm signal from the reionization and pre-reionization epochs (2009, unknown): “The radiative coupling is given by xα = SαJα Jc , (9) with Jc ≈ 5.552 × 10−8(1 + z) m−2s−1Hz−1sr−1 and Sα is a correction factor of order unity (Chen & Miralda-Escudé 2004; Hirata 2006; Chuzhoy & Shapiro 2007; Furlanetto & Pritchard 2006; Furlanetto et al. 2006).”
The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z≈ 8.6 (2010, background): “Alternatively, X-rays from supernovae or QSOs might have heated the IGM above the CMB temperature of ≈ 30K before reionization (Madau et al. 1997; Chen & Miralda-Escudé 2004).”
Detecting the Earliest Galaxies through Two New Sources of 21 Centimeter Fluctuations (2004, background): “…(defined as the spherical average of the number of photons hitting a gas element per unit area per unit time per unit frequency per steradian), andSα (Chen & Miralda-Escudé 2004) is a correction factor between 1 and 2 that depends on the gas temperature and accounts for the redistribution…”
21-cm fluctuations from inhomogeneous X-ray heating before reionization (2006, background): “Sα is a correction factor of order unity, which describes the detailed structure of the photon distribution in the neighbourhood of the Lyα resonance (Chen & Miralda-Escudé 2004; Furlanetto & Pritchard 2006; Hirata 2007; Chuzhoy & Shapiro 2007).”
The Evolution of the Intergalactic Medium (2015, background): “…surely motivate searches for this signal from earlier times as, unlike other probes of the z > 5 IGM, 21cm radiation is not just a reionization-era probe and has the potential to probe all the way to z ∼ 200 (Madau, Meiksin & Rees 1997; Chen & Miralda-Escudé 2004; Furlanetto, Oh & Briggs 2006).”
Wouthuysen-Field coupling strength and application to high-redshift 21-cm radiation (2005, methodology): “Incorporating the simplified model of the Lyα spectral distortion using the Voigt profile (e.g. Chen & Miralda-Escudé 2004) reduces the error to a factor of 6 1.9, as shown by the short-dashed curves.”
The Destruction of Cosmological Minihalos by Primordial Supernovae (2008, background): “It has been suggested that Ly photons from Population III stars are scattered by H in the early IGM, coupling its spin temperature to its kinetic temperature without heating the gas (Chen & Miralda-Escudé 2004).”